In a repressible operon, the repressor molecule
A) is the substrate of the metabolic pathway.
B) can repress the transcription of the operon on its own.
C) is a molecule made from the operon.
D) binds to the mRNA.
E) must be activated by a co-repressor.

Question

Quizplus · Accepted Answer

In a repressible operon, the repressor molecule must be activated by a co-repressor in order to bind to the operator region, which then prevents transcription of the operon. The co-repressor is usually a small molecule that is synthesized by the metabolic pathway that is regulated by the operon. The binding of the co-repressor to the repressor molecule causes a conformational change that allows the repressor to bind to the operator region and prevent RNA polymerase from transcribing the operon.

In a Repressible Operon, the Repressor Molecule